Abstract

Background:Higher socioeconomic position (SEP) has been associated with increased risk of breast cancer. Its relationship with earlier age of pubertal onset, a risk factor for breast cancer, is less clear.
Methods:We studied the relationship of SEP to pubertal onset in multiethnic cohort of 1237 girls aged 6-8 years at baseline. Girls in three U.S. cities were followed for 5-8 years with annual clinical examinations from 2004 to 2012. SEP measures were examined for associations with pubertal onset, assessed by breast budding (thelarche) and pubic hair development (adrenarche). Analyses were conducted with accelerated failure time models using a Weibull distribution, with left, right and interval censoring.
Results:Higher BMI% at entry to the study and black or Hispanic race/ethnicity were the strongest predictors of age at pubertal onset. A SEP Index comprised of household family income, mother's education and home ownership was an independent predictor of thelarche in adjusted models for all girls together and for white and Latina, separately, but not black, girls and the relationship varied by study site. The SEP index was not related to adrenarche in adjusted models. Overall girls from the lowest quintile of SEP entered puberty on average 6% earlier than girls from the highest quintile (time ratio=0.94, 95% confidence interval 0.91-0.97) in adjusted models.
Conclusions: Our results suggest that early life SEP may influence the timing of pubertal development.
Impact: Factors related to lower SEP in childhood can adversely affect early development in ways that may increase the risk of breast cancer.